Final answer:
Specificity, progression, and overload are key training principles for improving fitness.
Explanation:
Specificity in training principles means that fitness improvements are specific to the type of training performed, such as how walking benefits the lower body and cardiovascular system, while push-ups benefit upper body muscles. Progression principle involves gradually increasing stress to improve fitness without risking injury. Overload principle dictates adding workload to the current exercise regimen to enhance fitness.
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